Water that contains hydrogen sulfide is commonly referred to as sour water. Sour water can arise from a number of different industrial processes as well as occur naturally in some water sources, such as wells. Besides the smell and effect on the taste of the water, hydrogen sulfide can cause corrosion and can have a number of environmental and health effects. It would be desirable to be able to use well water in many drilling and fracturing operations in hydrocarbon formations. However, some well water contains significant amounts of hydrogen sulfide, which leads to corrosion problems and the like. The corrosiveness, malodorousness, and other deleterious properties of hydrogen sulfide make it desirable, and usually necessary, to remove this compound from streams containing it in some stage of processing. The treatment of such water is also necessary before discharging it to the environment to reduce the hydrogen sulfide content to acceptable levels.
There are several recognized ways of reducing or removing hydrogen sulfide from sour water. For example, current practices generally require use of a vessel with either direct steam injection or a reboiler and a condenser, known as a sour water stripper. The sour water is supplied to the stripper, and two effluent streams are discharged: a stripped sour water stream, and sour water offgas. The sour water offgas, which contains hydrogen sulfide, is commonly sent to a reactor to convert hydrogen sulfide to non-toxic elemental sulfur (e.g., a Claus unit). A conventional sour water stripper design for hydrogen sulfide removal is depicted in FIG. 1 including a sour water stripper (1) and a Claus unit (2). A sour water stream (3) and steam (4) are injected to a stripper vessel (5). Stripped sour water (6) is removed at the bottom of the stripper vessel, and a mixture of hydrogen sulfide and steam (7) are removed from the top of the stripper vessel, and supplied to a condenser (8), cooled by a cooling water supply (9). The cooling water can be recycled by a cooling water return feature (10). Condensed water (11) can be returned to the stripper vessel. Hydrogen sulfide gas (12) exits the condenser and is transferred to a furnace (13) heated to 1000 to 1400° C. An air stream (14) is also supplied to the furnace. The hydrogen sulfide gas then enters a Claus unit comprising multiple catalytic sections (15) and separators (16) which can produce elemental sulfur (17).
The process utilizing a conventional sour water stripper has several disadvantages associated with its use, for example, significant amounts of energy are required to produce the steam necessary to strip the hydrogen sulfide. Additionally, significant amounts of cooling water are necessary to condense the steam and produce the hydrogen sulfide-containing off gas stream. In constructing the stripper and other necessary equipment, care must be taken in choosing appropriate materials because of the corrosiveness of the hydrogen sulfide, as well as the elevated temperatures required.
There remains a continuing need for an improved method to remove hydrogen sulfide from sour water that overcomes the above-described technical limitations.